1. Field of the Invention
This invention relates to a laser device.
2. Discussion of Prior Art
Optical parametric generator's (OPG's) have been used to generate laser-like output within a certain spectral range. The OPG comprises a non-linear crystal material to which a pump source is applied. The spectral range is constrained by the pump source wavelength, the type of non-linear material used and the relevant geometry-type implemented. The output of an OPG is usually of relatively narrow spectral bandwidth, centred at a wavelength determined by the angle of the crystal axis relative to the pump to axis. Conventionally, the centre wavelength can be continuously tuned by altering the orientation or changing the temperature of the crystal, tuning taking place through consideration of the principle of conservation of momentum, namely phase matching in the terminology of non-linear optics. Normally, for a certain orientation of the crystal, only a narrow spectral range of signal and idler wavelengths satisfy the phasematch constraints, thus only a narrow spectral range of signal and idler wavelengths can be generated simultaneously. Attempts have been made to obtain broader spectral bandwidth output using dye or vibronic laser systems, but the dyes used in dye systems may be harmful and special safety precautions are required, while vibronic systems are complex to operate and the bandwidths obtained are small, typically less than 50 nm.